Compound and method to improve wrinkle resistance in fabrics, and fabric provided with said compound

ABSTRACT

The invention relates to a compound to improve wrinkle resistance in fabrics, comprising: a wrinkle reducing agent, comprising at least one fusible elastomer, and a liquid carrier for carrying said agent and a salt composition for physical crosslinking said fusible elastomer. The invention also relates to a fabric provided with said wrinkle resistance improving compound. The invention further relates to a method of improving wrinkle resistance in a fabric by use of such a compound.

The invention relates to a compound to improve wrinkle resistance infabrics, comprising: a wrinkle reducing agent, comprising at least onefusible elastomer, and a liquid carrier for carrying said agent. Theinvention also relates to a fabric provided with said wrinkle resistanceimproving compound. The invention further relates to a method ofimproving wrinkle resistance in a fabric by use of such a compound.

In Wear Wrinkle Resistance (IWWR), as the name suggests, means theproperty of a set fabric, e.g. cotton, which enables it to resistformation of wrinkles, especially during wear of the fabric. IWWR can beassessed by measuring the ability of a set fabric to resist theformation of wrinkles. Wrinkle resistance is generally assessed byWrinkle Recovery Angle (WRA) tests. A well-known standard test is theAATCC method 66-1998. Such tests assess the ability of fabric which isset in a flat state to recover this flat state after being folded,subjected to a temporary load, preferably 500 g during 60 s, and thenreleased. The assessment is carried out by measuring the recovered angle(WRA) after a given time (commonly 5 minutes). The greater the angle,the better the recovery. Angles are measured in both the warp and theweft direction and added up to give a final result of the assessment. Aperfectly elastic material would give a WRA of 360 degrees. A perfectlyviscous material would give a WRA of 0 degrees.

Compounds for reducing wrinkle formation in fabrics are known. TheAmerican patent publication U.S. Pat. No. 5,532,023 discloses, forexample, a wrinkle reducing composition which can be applied to fabrics.The composition comprises a wrinkle reducing agent, comprising aneffective amount of silicone and an effective amount of film-formingpolymer, which agent is dispersed in a liquid carrier. In particular,the disclosed composition is adapted to impart a lubricating property orincreased gliding ability to fibers in fabric, particularly clothing.This gliding effect between the fibers is particularly caused by thesilicone. Deformation of the clothing reduces the friction between thefibers of the clothing, which results commonly in a decreased energydissipation at the fibers and (thus) also a relatively good and easycontra-deformation (recovery) of the fibers in the original state.However, decreasing the friction between the fibers of the clothing willalso facilitate the formation of a wrinkled state of the clothing.Application of the disclosed composition on clothing leads commonly to aWRA of up to about 200 degrees.

It is an object of the invention to provide an improved compound whichimproves significantly wrinkle resistance in fabrics, withoutfacilitating the formation of a wrinkled state of the fabrics.

This object of the invention is achieved by a compound as mentioned inthe opening paragraph, characterized in that the compound furthercomprises at least one salt composition for physical crosslinking ofsaid fusible elastomer. Crosslinking provides elastic linkages betweenmolecular chains of said fusible polymer to prevent them from slidingpast each other irreversibly, which would lead to dissipation of energy.Such junctions provide an additional source of energy for recovery.Physical crosslinking provides a relatively strong elastic bindingbetween the chains of the fusible elastomer. In particular, cations ofthe salt composition form an intermediate between chains of said fusibleelastomer. Thus, said cations of the salt composition provide—incombination with the fusible polymer—a relatively strong elastic bindingbetween fibers of said fabric with a certain memory, which enables it torecover relatively easily after bending or creasing of the fibers.Application of the compound according to the invention will commonlylead to a WRA of significantly above 200 degrees. The fusible elastomersused may be e.g. polyurethanes, polybutadienes, and acrylate copolymers(of, for example, butyl acrylate and acrylic acid, preferably in a ratioof 80:20), as long as said chains of aforementioned elastomers can belinked by cations of the salt composition. The liquid carrier used inthe compound of the present invention is preferably a system comprisingwater. Optionally, in addition to water, the carrier may compriseanother liquid solvent which is well soluble in water, such as analcohol.

Preferably, the salt composition comprises polyvalent cations.Polyvalent cations having a multiple positive charge, e.g. 2+ (zinc,calcium, magnesium) and 3+ (iron, aluminium), are in fact capable ofcrosslinking multiple chains of said elastomer whereby said physicalcrosslinks are formed. In a preferred embodiment, the salt compositioncomprises at least one of the following ions: zinc, calcium and borateions.

The salt composition is preferably insoluble in the liquid carrier atroom temperature and sufficiently soluble in the liquid carrier forphysical crosslinking of said elastomer at a relatively hightemperature. The mixing of said wrinkle reducing agent with said saltcomposition according to the invention will commonly have consequencesfor the stability of the emulsion because crosslinking (or sometimeseven a change in pH as a result of the addition of the salt) can causeparticles of said compound to flocculate, thereby precipitating from thesolution. This problem can be solved by applying an insoluble saltcomposition. If the temperature of the compound is subsequentlyincreased, the fusible elastomer will melt and the salt composition willdissolve and will finally crosslink the chains of said elastomer. Notethat for effectuating a reaction (physical crosslinking) between saidelastomer and ions of said salt composition it is necessary to ionize,and thus dissolve, said salt composition to a sufficient degree.

Preferably, the compound according to the invention comprisesmicrocapsules which are provided with said salt composition, either asan aqueous solution or in a solid state. Said microcapsules are commonlystable at room temperature and prevent premature contact between saidsalt composition and said fusible elastomer. When the temperature ofsaid compound has increased sufficiently, the microcapsules will deformin such a manner that the salt composition will contact said fusibleelastomer. Deforming of said microcapsules may be realized, for example,through melting, dissolving, or tearing open.

In a preferred embodiment, the content of the agent in the liquidcarrier is between 2 and 60% by weight, preferably between 5 and 30% byweight, more preferably substantially 12.5% by weight. Between or atthese values, a good dispersion of the active in the liquid carrier canbe obtained and maintained. If said percentage of 60% is (significantly)exceeded, a sticky, non-controllable dispersion is usually obtained.

In another preferred embodiment, the elastomer has a softeningtemperature between 50 and 100° C. in the presence of water. Easysoftening of the elastomer at an increased temperature commonly resultsin an easy provision of the yarns of the fabric with the compoundaccording to the invention. The viscosity of the softened compound isrelatively very low, which means that the polymers do not interfere withthe wrinkle removal from the fabric, e.g. during ironing of said fabric,as long as the fabric is relatively hot. When the fabric cools down, thecompound according to the invention solidifies to form an elastic filmaround and between the yarns or individual fibers, thereby inducing adegree of elasticity in the treated fabric. This in turns improves theWRA value substantially.

Preferably, the fusible elastomer is provided with one or more effectivegroups, more preferably comprising of least one of the following groups:hydroxylic groups and carboxylic groups. The effective groups can bebonded to an ion, mostly a cation, thereby forming a complex of an ionand more polymer chains. The formed macromolecule is also known as anionomer. It may be obvious to those skilled in the art to applyeffective groups other than those of the two examples mentioned afore.It may therefore be clear that within the scope of the claims elastomerswith other effective groups may alternatively be applied. The binding ofat least two chains of an elastomer to an ion of said salt compositioncan be illustrated in the two following non-restrictive examples.

In the first example, two chains of a copolymer of acrylic acid arephysically crosslinked by a bivalent zinc-ion:

wherein R1 and R2 are parts of the chain of a molecule of theaforementioned copolymer. In this example the carboxylic groups functionas effective groups for physical crosslinking. In the second example twochains of a (co)polymer provided with alcoholic groups as effectivegroups are bound by a borate-ion.

wherein R3 and R4 are parts of the chain of a molecule of theaforementioned (co)polymer. The borate ion thus functions as anintermediate for physical crosslinking of said two chains.

In a preferred embodiment, the molar ratio of (cat)ions of said saltcomposition to the effective groups of the fusible elastomer issubstantially situated between 1:4 to 1:6, and is preferably 1:5. Themolar ratio of 1:5 is in particular suited for a bivalent (cat)ion incombination with said fusible elastomer since a slight excess of polymermolecules are present compared to the added (cat)ions.

The compound is preferably provided with additives, such as asurfactant, stabilizer, perfume, anti-bacterial additives, or siliconesfor improving gliding between the fibers of the fabric, etc., as long asthe additive does not interfere with the primary function of thepolymer. The use of additives in a compound according to the inventioncan be very suitable when applying the compound to a fabric by means ofa domestic appliance, such as an iron. The additives may also be appliedduring a washing cycle. However, to prevent premature flocculation ofthe compound according to the invention, it is not desirable to add boththe salt composition and the fusible elastomer to a washing machine.

The invention also relates to a fabric provided with said wrinkleresistance improving compound. In a preferred embodiment, the compoundcomprises at least one ionomer, which ionomer comprises: ions,preferably polyvalent cations, and said fusible elastomer, whereinchains of said fusible elastomer are physically crosslinked by the(cat)ions. As was mentioned above, the ionomer may be created by anincrease of the temperature that melts the elastomer. After cooling downthe ionomer remains in the fabric as an elastic substance on and inparticular between the fibers, resulting in a relatively high wrinkleresistance.

The invention further relates to a method of improving wrinkleresistance in a fabric by the use of said wrinkle resistance improvingcompound comprising the steps of: A) applying the compound to thefabric, B) removing the wrinkles in the fabric, and C) permitting theliquid carrier to evaporate at least partially. The amount of agenttypically applied, particularly sprayed, onto the fabric is preferablyfrom about 0.5 to about 10% by weight, more preferably from about 2 toabout 5% by weight with respect to the fabric. Once an effective amountof compound has been sprayed onto the fabric, the fabric is stretched orsmoothed by hand according to step B). After the effective amount ofcompound has been applied to the fabric and the latter has preferablybeen stretched, the liquid, in particular moisture, is permitted toevaporate at least substantially. The evaporation may occur both in apassive way or in an active way through an increase in the temperatureof the fabric. Evaporation of the moisture is commonly relevant, as theparticles of the fusible elastomer will stick together and thus form asolidified sheath around the fibres and yarns of the fabric.Furthermore, evaporation of moisture will commonly also result in stressrelaxation in the yarns of the fabric. A decrease in the stored energywill maintain the fabric in its set, i.e. flat, state.

Preferably, the application of the compound to the fabric according tostep A) is realized by means of a domestic appliance. Examples of suchdomestic appliances are a washing machine, an iron provided with acompound spraying reservoir, and other spraying devices for a compoundaccording to the invention. In a more preferred embodiment, an iron isprovided with two separate spraying reservoirs. A first reservoir can befilled with an aqueous solution of the salt composition and a secondreservoir can be filled with a dispersion of the fusible elastomer.Separation of both ingredients of the compound according to theinvention prevents flocculation of compound in advance. Thus, the twoingredients will contact each other after the spraying of bothingredients on said fabric. According to this embodiment, ionomers willtherefore only be formed on the fabric.

In a preferred embodiment of the invention, the removal of the wrinklesin the fabric according to step B) is realized by means of an iron at anincreased temperature compared with an environmental temperature. Inthis way step C) will commonly be applied during application of step B).Thus, the increased temperature will lead both to an acceleratedevaporation of applied liquid and to a softening of the fusibleelastomer. Cooling down of the fabric results commonly in an elasticprotective layer formed around the stretched yarns of the fabric,wherein the layers are bound to each other by elastic bridges.Deformation of the fabric after applying the method according to theinvention will temporarily lengthen said elastic bridges, which willattempt to bring the yarns to their original stretched, non-wrinkledstate during a certain time.

In a final preferred embodiment, the application of the compound on thefabric according to step A) is realized in that the salt composition andthe wrinkle reducing agent are applied sequentially. Sequentially addingthe ingredients of the compound to said fabric may be realized, forexample, by the aforementioned iron provided with two separatedreservoirs. It is also possible to add one of the ingredients, e.g. thesalt composition, to the fabric during a washing cycle. The fusibleelastomer can be sprayed on the fabric provided with said saltafterwards. This is to prevent flocculation (crosslinking) of theingredients before they are applied to the fabric.

The invention may be further illustrated by way of the followingnon-restrictive example.

EXAMPLE

A 12.5% (by weight) solution of latex of poly(butyl acrylate-co-acrylicacid) 90:10 in water was prepared (Composition A) by dilution to therequired level. A 2% solution of zinc acetate dihydrate (Aldrich) wasprepared in water (composition B). Composition B was then sprayed onto apiece of fabric (cotton type 407) such that the total pick-up based onfabric weight was 15%. This led to an additive pick-up of 0.3% based ondry fabric weight. After being dried in air, the fabric was sprayed withComposition A such that the total pick-up based on fabric weight was40%. Hence the amount of polymer based on fabric weight was 5%. Theratio of zinc ions to the acrylic acid groups was 1:5 (molarequivalents). The fabric was then ironed to dryness with an iron set toa temperature suitable for cotton. After conditioning of the fabric for24 hours, the WRA was measured according to the standard AATCC method66-1998 for cut-out pieces of the specified size (40 mm×15 mm), in boththe warp and weft directions. The average WRA value obtained fromfabrics treated as above was compared with WRA measurements carried outon fabrics ironed without the application of any additives (referencevalue) as well as fabrics ironed after the application of 5% based onfabric weight of only poly(butyl acrylate-co-acrylic acid) 90:10.

The WRA reference for said fabric is 140°. The resulting WRA for theused poly(butyl acrylate-co-acrylic acid) latex according to compositionA was 1970. However, the resulting WRA of the used poly(butylacrylate-co-acrylic acid) latex in combination with said zinc ionsaccording to composition B was 204°.

1. A composition to improve wrinkle resistance in fabrics, thecomposition comprising: a wrinkle reducing agent including at least onefusible elastomer having one or more effective groups for bonding to anion; a liquid carrier for carrying said wrinkle reducing agent; and atleast one salt composition having cations for physical crosslinking ofsaid fusible elastomer to provide elastic linkages between molecularchains of said fusible polymer, wherein the cations of the at least onesalt composition in combination with said fusable elastomer provide astrong elastic binding between fibers of the fabric with a certainmemory, which enables the fabric to recover relatively easily afterbending or creasing of the fibers.
 2. The composition according to claim1, wherein the at least one salt composition comprises polyvalentcations having a multiple positive charge.
 3. The composition accordingto claim 2, wherein the polyvalent cations of the at least one saltcomposition are selected from at least one of zinc, calcium, and borateions.
 4. The composition according to claim 1, wherein the at least onesalt composition is insoluble in the liquid carrier at room temperatureand sufficiently soluble in the liquid carrier at a relatively hightemperature for physical crosslinking of said elastomer.
 5. Thecomposition according to claim 1, further comprising microcapsules whichare stable at room temperature to prevent premature contact between saidsalt composition and said fusible elastomer, the microcapsules areprovided with said at least one salt composition.
 6. The compositionaccording to claim 1, wherein the content of said wrinkle reducing agentin the liquid carrier is between 2 and 60% by weight.
 7. The compositionaccording to claim 1, wherein the elastomer has a softening temperatureof between 50 and 100° C. in the presence of water.
 8. The compositionaccording to claim 1, wherein the fusible elastomer is provided with theone or more effective groups selected from at least one of hydroxylicgroups and carboxylic groups.
 9. The composition according to claim 8,wherein the molar ratio of cations of said at least one salt compositionto the effective groups of the fusible elastomer is substantiallysituated between 1:4 to 1:6.
 10. The composition according to claim 1,further comprising additives including a surfactant, stabilizer, orperfume for improving gliding between the fibers of the fabric.
 11. Thecomposition according to claim 1, wherein the physical crosslinking isbetween portions of said fusable elastomer.
 12. The compositionaccording to claim 8, wherein the at least one salt composition and saidfusable elastomer form an ionomer as a complex of an ion and two or morepolymer chains with an increase of temperature sufficient to melt saidfusable elastomer.
 13. The composition according to claim 1, whereinsaid fusable elastomer comprises a solution of poly(butylacrylate-co-acrylic acid).
 14. The composition according to claim 1,wherein said fusable elastomer comprises a solution of poly(butylacrylate-co-acrylic acid) 90:10 in water.
 15. The composition accordingto claim 1, wherein the at least one salt composition comprises asolution of zinc acetate dehydrate.
 16. The composition according toclaim 1, wherein the at least one salt composition comprises a 2%solution of zinc acetate dihydrate in water.